Zout is great on lab coats for removing all sorts of stains. I like the previous idea of staining a scrap and trying various methods before experimenting on the quilt. Rit dye co. makes a color remover. Another option mentioned is Oxyclean- dissolved in Hot water dabbed with a cotton swab. Be sure to rinse well as it can be a bit tough on fibers over time. You don't want to bleach out the backing so don't soak the stain. Just dab and rinse. Please let us know what works for you. JoAnns used to have a series of stain removers- small bottles with different formulas for specific stains. Don't know if they still do. Ask a coffee shop what they use on their clothes?